In a microprogrammed digital computer or data processor, microwords are read from an internal control storage unit to provide the internal processor control actions which are needed to execute the system or processor instructions obtained from the user's software program. The microwords are read from the storage unit and set into a control register one at a time. Each microword consists of multiple binary bits, some or all of which may be organized into plural-bit control groups or control fields. The control register drives a decoder mechanism which produces the elemental control point signals which, in turn, control the various data flow gates and data manipulation mechanisms located in the data processor. Each microword controls the internal operation of the data processor for one microword cycle. Several microwords are normally needed to execute a processor instruction. Some processor instructions require only a few microwords, while others require many microwords to complete their execution.
The current trend is to fabricate the principal sections, including the microword control unit section of a data processor on large scale integration (LSI) integrated circuit chips. The overall objective is to increase the number of data processing functions that can be provided on a single integrated circuit chip, with the ultimate goal of providing a complete data processor or digital computer on a single chip. Currently, the best technology for packing the largest number of circuits onto a single chip is the so-called metal oxide semiconductor field effect transistor (MOSFET) technology. Such technology makes possible a very high circuit density on an integrated circuit chip. Unfortunately, MOSFET circuits have a somewhat slower operating speed than do circuits fabricated by means of other integrated circuit technologies, such as, for example, the so-called bipolar integrated circuit technology. Thus, it would be desirable to find ways to increase the operating speed of data processor mechanisms which employ MOSFET circuits. Also, even though the MOSFET technology provides a high circuit density, care should be taken not to be wasteful of circuit space. In other words, it remains desirable to provide circuit mechanisms which reduce the amount of circuitry required on the integrated circuit chip.